Radioactive
by PuffleHuffWriting
Summary: Natasha Romanov has dealt with every obstacle life has thrown her with an iron will- Until the impossible hits her, Brutasha fic with a side of Steve/OC and a heavy Family!Avengers vibe- Post Ultron
1. Chapter 1

**I needed a Brutasha fic- had this one bouncing around my brain distracting me from my others so I started it too.  
AU, obviously.  
Enjoy!**

* * *

This sensation was a familiar one. Like the blunt force of a nearby explosion that set your ears to ringing. The wind was gone from her chest as well. The room was spinning. Natasha closed her eyes to stabilize herself. To gain her control.

"That is simply not possible." She replied quietly, curling her knees to her chest and pulling the exam gown down to cover herself.

"Well, Agent Romanoff, I'm not sure what you _want_ me to tell you..." The young doctor trailed off. Natasha liked the kid- she was a good fit for their team. A young, smart, freshly graduated doctor who just happened to have actual healing powers. It didn't take Tony and the other's long after she hit Avenger radar to decide to bring her on board. She tagged along on some missions, often able to keep civilian damage to a minimum- saving countless lives in the carnage Ultron had caused. But she did have a habit of being a bit too formal when in her professional mode; however in this moment she was going to have to let it go.

"I had a tubal ligation when I was still a teenager." She interrupted.

"I read all of ya'll's files when I took the job." Dr. Jennifer Ford reminded her patient, her slight Tennessee accent coming up at her annoyance. "I am aware. But you heard that as well as I did. It's a good, strong heartbeat. Clocked it at around a hundred and seventy four beats per minute."

"I don't-" She hugged her knees tighter and the young doctor sat down and put a hand on her friend's back.

"Let me take a few samples of your blood. Run a couple tests. I'll see if I can find a logical explanation for the how. Until then though, I'm afraid I'm going to have to write you off work. At least missions and active training." She said quietly. Her dark eyes watched the redhead, hoping she would give some signal of understanding.

"What do I tell the team?" She asks quietly. Jennifer took a bottle of pills from a cabinet and tossed them to the agent on the exam table.

"I'll take care of that. You take those vitamins until we can get you some actual prenatals. And don't worry about the team, after all, you did tell them you weren't feeling well when you decided to ask me to look you over." Jennifer replied gently. "I doubt they'll be too nosy. Except maybe Clint."

"Clint can know." She said, "And no, he's not the father." She added quickly.

"Didn't think he was. I've seen him with Laura." She said with a grin, humored at Natasha's little burst. She patted her friend again and stood up, leaving her little clinic room so Natasha could take a moment and change.

Natasha didn't move at first. She stared ahead at the blank white wall, thinking of everything and nothing. It had only been six weeks since they defeated Ultron. The preliminary test on hormones Dr. Ford ran put her at eight weeks. She couldn't help but wonder how a pregnancy could survive some of the trauma she'd received during that fight. It really didn't make since that she was even able to conceive in the first place, but for it to survive all that, it really did seem impossible.

It was while thinking on the impossible she remembered she was all alone.

Bruce was gone.

She'd begged Hulk to turn the quinjet around. To come home. But he had simply shut the communicator off and kept flying- Why she didn't know. Bruce was filed a missing person, and Tony had him made a top priority find in every country he could manage. There was no sign of him anywhere. She slid one leg away and touched her abdomen.

Bruce was the one who had always wanted kids.

She'd known that from the moment she met him in his little jungle shack. He was a kind and caring man, and she knew he'd be a very loving father. Yet, when she first made a move on him, his protest had been that he couldn't have that life. He couldn't have children. Her reply had been a very quiet 'me neither'. It was one of their defining moments. A bonded pain.

From there, most of their relationship was a secret; Stolen moments and late night trips through the tower to each other. And apparently, this was their end result. Slowly, she stood on shaky legs, afraid of something for the first time in a long time. Once her clothes were back on she peaked out the door into the main medical bay of the tower, where she found Jennifer at her computer, ordering more supplies for prenatal care.

"Doesn't Tony see anything you order? Like, to authorize it?" Natasha ask, looking over her shoulder.

"Nope." She replied dully, hitting the 'submit' on the website. "That is part of my deal when I was negotiating my terms." She explained. Natasha made a small nod of understanding, arms still wrapped around her middle.

"So-" Natasha started, then looked up, then back to the other woman, "Is there anything I should know? Like, that I have to change?"

"No sushi, no unheated deli meats, no rare meat, be careful about certain seafood..." She stopped and thought. "I'll get you a list. Go head up and maybe rest. Maybe shower. Relax." She gently guided her down the hall. "And if you need your doctor, call down and I'll come up. If you need your friend- At least give me enough time to spin your blood down and run my tests."

"Thanks, Jen. I'm glad we have you. Dr. Banner did good enough, but that MD was not his strongest point." Natasha said, taking a deep breath as she thought back to a mission where Bruce had to reset her shoulder. "But wait- Isn't it Thursday?"

"Yeah, so?" She quirked an eyebrow.

"Do you not do 'pop culture Thursday' anymore?" Natasha ask, her tone hinting in a way she knew Jennifer would pick up on- and be annoyed by.

"I think, if you need the company, your needs will out weigh Steve's need to be brought into this century." She laughed.

"We just have better bedside manner in the south, hospitality is a requirement" She laughed, letting Natasha head upstairs.

* * *

"AY!" Sam shouted from the practice field, catching Steve's shield in the air and slinging it back to the man on the ground, who used it to burst the last of the practice droids Tony had built for team building. When they powered down, a buzzed sounded and Sam Wilson collapsed his wings and thumped down to the floor. He nodded behind the taller man to where the observation bench was. "Jen is here, Cap." Steve snapped a quick look over his shoulder and then back to Sam.

"I hope Natasha is okay." He replied, moving past his friend to start clean up.

"What's the movie for tonight, anyway?" Sam pressed. Steve did not look back up to him when he answered.

"I don't know what you're-"

"We all know, man. No judgement, at all. Jennifer is hot. Smart. Brings some much needed 'black-girl-magic' to the team. And she likes you, too. Look at her." Sam replied. He looked over Steve's shoulder again and waved, and she waved back, grinning when Steve also turned around and gave a small wave. Steve froze when he turned back, and stared at Sam, his brow furrowed a bit.

"I don't really want to discuss this." He said quietly. Sam gave a half nod and continued to help clear away their practice gear.

"You may not want to discuss it, but she's coming down. So try not to look so sour." He said, leaning into Steve's shoulder as he walked by. "Doctor Ford!" He greeted.

"Hey Sam. Ya'll have a good session?" She replied politely. Steve turned around and propped against a small brick wall. Sam had replied as he kept walking, so she came on over and propped next to the tall blond. She waited for a moment for him to speak.

"Doctor Ford." He greeted, his overly formal tone almost making her laugh.

"Captain Rogers." She replied. He looked over at her, arms crossed, his blue eyes meeting her shining dark brown ones. He stayed slightly tensed, but Jennifer seemed used to his discomfort in some moments- She'd learned to find it almost enduring. "Listen- I had already rented the first season of Star Trek: The Next Generation, but I really think I'm going to have to camp out down in Agent Romanov's rooms tonight. If you want to get started, you're welcome to. My dad was a huge trekkie, I've seen the whole series twice. I can set it up in your player, if you want."

"Is Natasha alright?" He ask, concerned. He did not answer the question about the television.

"She will be." She nodded.

"I have the upmost faith in her physician." He replied with a smile.

* * *

Natasha lay on her couch, her feet propped over Jennifer's lap, head on Clint's shoulder. Clint had called Laura, who insisted he stay there for a bit and make sure Natasha was okay. So the three of them sat in heavy silence, allowing the spy to think. After quite a long time of silence, she let out a slightly snubbed sigh and said, "What if we never find him?"

"Bruce wouldn't keep himself from you on purpose, Nat. I think we all know him better than that." Clint assured her.

"But he didn't know. And I know he was mad at me. They both probably are- Him and the other guy." She croaked again, swallowing the thick emotion in her voice.

"Why would either of them be angry with you?" Jennifer ask, confused. She was not quite as privy to their relationship as the archer had been, and had only just recently learned that they were even involved. She had said it was probably going to be easier for her to treat her if she had all the information. Especially since Bruce had his mutation.

"I threw him." She said dully. "I kissed him, then I threw him. He was scared of changing again. He had been losing control on his changes. And I threw him." She shook her head. "I told him I adored him and threw him off a cliff."

"Ah." Jennifer replied, glancing over at Clint, who gave her an 'no, I know' sort of look. The sound of a beeper went off and made Jennifer jump, the other two did not react. She took her tablet out of her pocket.

"I need to go check on some of your results. Looks like a couple may be done." She gently rose and moved Natasha's feet before placing them on the couch where she had been. Once the door to Nat's apartment swung shut, Clint sat his best friend up.

"I know what will cheer you up..." He said, and Natasha picked up on the hint of mischief in his voice.

"You have most of my attention." She said, looking him over.

"Little Jennifer's birthday is next week. And Pepper tells me that she has not seen most of her family since she signed on with us. So we were thinking of flying them up and having her a small, sweet, birthday of sorts." He explained.

"Go on." She said, knowing him well enough to know there was more to add.

"Well, I was thinking- We could use that opportunity to get Captain Should-be-more-obvious to actually make a move. And I know you've been trying to find him a date for a while now. We all know he's got something for her. We could use it." He informed her.

"Oh, I like this. Meddling in Steve's life is one of my favorite hobbies." She leaned back and smiled. "I could use something non-lethal to focus on. Thank you." She sighed.

"No problem." He laughed, and for a moment she joined him in the humor. They fell back into a comfortable old silence for a moment, before Natasha spoke out softly.

"Clint. Promise me, if we can't find Bruce- That you and Laura will take it." She didn't move, but Clint went rigid.

"Nat-"

"I asked you to promise me." She said firmly.

"If that is what you still want, and we don't find Banner, we will take it." He confirmed. He knew her better than to think she'd really give her child away easily, but he also knew her insecurities as well. He squeezed her shoulder. "It'll be okay, Nat. Banner can't hide forever. Especailly since he's one of Tony's people. Tony does not give up on his people."

"That's true. I'm glad we have him, these days." She said, yawning.

"Come on, let me tuck you in." He said gently, using the same voice he used when putting his children to bed.

* * *

 **So, had the idea for this Nat-Bruce centered fic but I also wanted some drama so I invented a love interest for Cap. Sue me. :)**

 **I hope you enjoyed the start of this! PLEASE review and let me know what you think.**


	2. Chapter 2

**I am so happy so many people are excited about this. I wanted to take this chapter to expand a little on my OC, but don't worry. There is plenty of Nat coming- and eventually Bruce too :)**

* * *

Jennifer had been looking over chem levels in Natasha's blood for a few moments now, trying her best to form some sort of hypothesis. She had a few samples of Banner's blood and tissue left in cyro, and had one vile of blood out to start a few experiments on. But she couldn't help but wonder- Did they have any of his notes?

Quickly, she grabbed her phone from her pocket and opened a new text message.

 **Pepper- Did Tony keep Bruce's hand written notes about his precursors to his gamma experiments?**

She sent the message before she had time to change her mind. Pepper was probably who she would consider her closest friend these days, and the young doctor trusted her. She smiled when the bubbles appeared almost instantly showing the redhead was typing, with a reply coming within seconds.

 **They're in a box on the third shelf down in the storage closet in Banner's lab. I think it says 'code green' or something like that on the side.**

Jennifer smiled, thankful her friend knew her well enough after the last couple years that she didn't ask too many pressing questions. She sent a quick thank you and headed off down toward the lab Banner had claimed, down at the end of the hallway from her own and the medical rooms. She found herself trying to be silent, even though she knew there was no one else even on this floor at this time in the evening, not that the other Avengers frequented the so called 'science level' wing of the compound.

The lab itself was spotless from disuse, and the only light came from the dim tank where Bruce's fish swam oblivious to her presence. She looked on the clipboard on the wall as she passed, making sure that someone had been through to feed them today- Sure enough Vision had signed off that he'd taken a turn caring for his missing teammate's pets. She quickly came over to the supply closet Pepper indicated and pulled the chain, lighting the small room.

Sure enough, about waist level, was an old copier paper box with the words 'Code Green' scribbled on the side in blue ink sat at about waist level. She pulled it out slightly, popping the lid off just enough to peak inside. There were a few journals, and composition books, as well as file folders and sample slides. She smiled again to herself at her success.

She hoisted the box up onto her hip and clicked the closet light back off before heading back down to her own lab, where she took all the material out and organized it around on the counter, hoping to flip through and find something that would help.

Bruce had been looking into the serum that made Captain Rogers into his enhanced self, not so much for the military aspects, but for the fact that it had cured several genetic diseases that Steve had been burdened with before it was administered. She opened each notebook, journal and file, lining them up by the dates inside, and began reading. She had found that Bruce had several different hypothesis for duplicating the experiment's results, and had tried a few on himself before the gamma accident.

Jennifer had just began to read about a combination of chemical compounds and stem cells Banner had tried formulating when her phone chimed that a text had come through. She sighed and took her phone from her back pocket to see what the notification said.

 **Do you have a minute?**

She read the message before the name, and yet, without having to look, she knew who it was from. Jennifer closed her eyes. She tried not to be annoyed, but her stomach ached at the anxiety that came with such a should be simple question.

 **Sure. What's up?**

The reply was almost instant.

 **Where are you? Can we talk in person? I don't like these.**

Jennifer swallowed thickly but sent back a quick response.

 **Sure. I'm in the med bay. Main lab.**

She pressed send before she lost her nerve and laid her phone down on the table beside a stack of research notes. She shook her hands to calm her nerves and took a hair tie from her wrist, gathering her thick, dark brown curls into a messy bun on top of her head. She went back to reading, the older doctor's notes, waiting for the door to open. She jotted the blood levels from labs Bruce had done on himself after this experiment to compare later, and was still scribbling when the door opened.

"Doctor Ford." Came her usual greeting.

"Captain Rogers." She replied, glancing up from her notes as he sat down on a stool on the other side of the counter from her.

"You said you weren't busy." Steve said, sounding a bit unsure of himself.

"No, I said I had a minute." She replied with a light smile of amusement. She took a sticky note from her stack and placed it over the last time she'd read and then looked up a the handsome solider across the table. "And I do. This is more of a 'on my own time' sort of project." She closed the journal and watched him, waiting.

"Are you sure?" He ask, his crystal blue eyes searching her face before meeting her deep chocolate brown ones.

"Mmm" She nodded.

"I was just thinking- We should probably talk about... You know." He sputtered.

"I think I need you to be just a smidge more specific, sugar." She laughed when his face turned red.

"That night. At Stark's party. Before Ultron crashed it." He clarified, although she didn't actually need it. Truth be told, Jennifer had wondered if he'd ever want to talk about that.

"Alright." She agreed, sitting forward and propping her chin on her hand, elbow on the counter. "Talk, Captain."

Steve looked even more pink than before.

"Look, Jen." He cleared his throat, "I haven't, done anything like this, in like, close to a hundred years. Help me a little."

"You kissed me at Tony's party." She restated the fact. "On the balcony. And you said you wanted to talk to me. But then all hell broke loose. So- Is this the same talk? Or is this a talk to take back that desire to talk?" She blinked at him, a kind smile spread on her face.

"You're very beautiful." Steve said, and Jennifer felt her ears burn. "And I really like you." He added, but he paused. She was afraid of this.

"But?" She ventured.

"No 'but', I'm just bad at this." He laughed at himself. She joined in a little as well.

"It's cute, everyone sees you as so confident." She tilted her head.

"I don't think anyone ever sees me, honestly." Steve confessed. "Its a very idealized version from propaganda. Which, let's be honest. I'm not living up to."

"You sell yourself so short." She comforted. "Just tell me what you had wanted to say that night. I've been waiting for weeks to see if you'd even want hang out with me again. I miss that."

"The whole team keeps asking me about that." Steve confessed.

"Thursdays?" She guessed.

"Who knew they all knew?" He snorted.

"We all live together, man. Separate apartments, but its a compound. Close quarters." She rose from her stool and came around the counter, hopping up on one next to Steve and spinning it so she sat facing him, propping again on her elbow. "But there wasn't really anything to know, was there? Binge watching television, movies, listening to albums- just catching you up with the world."

"All those Thursdays meant a lot to me." He said quietly. She smiled. "I especially liked when you'd fall asleep on my shoulder while watching things." He spoke more quietly. Jennifer blinked at him, surprised he said such a thing.

"Steve?" She questioned, knots forming in her stomach.

"I- I don't know. For now, really, I just was wondering if maybe we could go back to spending time together. Like we did?" He ask. Jennifer felt like a lead weight hit the bottom of her gut, but yet again, she smiled.

"I would love that." She replied gently, giving a small nod. She leaned back, now realizing this was going back to being just as awkward as it was before- If not a bit worse. Steve seemed to want to clear the air without addressing anything. She sighed inwardly, but decided not to allow any of that emotion through. At least he wanted to be her friend again. She could live with that.

"I'll let you get back to work, then." He said, standing up abruptly, then before she could reply he left the lab. She swallowed again, taking a deep breath to calm her nerves, then she reopened the journal she'd been reading before.

* * *

Early the next morning, Jennifer let herself into Natasha's apartment, where she found Clint making pancakes. He greeted her, asking her if she wanted him to add her a few, which she gladly accepted. Natasha sat in the living room, sipping a sprite through a straw. Jennifer handed her the legal pad she'd been taking notes of Bruce's research on.

"What is this?" Natasha ask, flipping through the pages Jennifer had filled.

"Your answer!" She relied cheerfully.

"Did you even sleep?" Natasha questioned, quirking an eyebrow at the other woman.

"I actually don't need to for two or three days at a time, if I don't want to." She confessed. "It's one of my..." She gestured about into the air. "But look-" She took the notes and flipped a few pages in. "See here? This is your white blood cell count at baseline, before I started, when Tony built the med bay and made y'all's files. This is from the other day. You can see it, as well as iron, vitamin D, and a few other things are higher now."

"Okay?" She said, brushing a stray strand of her long red hair back. Clint came in and propped himself on the wall beside his friend, listening.

"Bruce was experimenting on himself. To duplicate the serum Stark's dad and that team used on Steve back in the forties. Right?" She looked at her coworkers, who both nodded slightly, waiting. "This is about to get a little personal." She warned, glancing from Natasha, to Clint, and back.

"He stays." Natasha confirmed.

"Bruce was experimenting on himself, and he did a couple different versions before he decided to give radiation a go. He marked them down unsuccessful, but really they were just _less_ successful. Not failures. And This one here..." She flipped the pages again, "With the stem cells, chemical compounds. It is extremely effective for cellular regrowth. In fact, I'd argue that this is what kept him from dying from radiation poisoning."

"So, how does that effect Nat?" Clint wondered, crossing his arms across his chest.

"Prolonged sexual exposure." She answered.

"What?" Natasha demanded.

"I told you it was going to get personal. But he changed his own DNA more than once. And as many things can do- Unprotected sexual exposure gives you doses. You were dosed too. In such a way that it healed the cauterization of your Fallopian tubes." She explained, almost excited. Natasha seemed to be trying to piece what she'd just been told, but Clint looked a bit green himself.

"Oh." Natasha said quietly.

"Wild, huh?" She said.

"You could say that." The spy replied. "But I guess when you explain the science behind it, at least I have my answer for 'how'."

"Well, then." Clint said, trying to make the air in the room less awkward. "How about we eat pancakes? I could really use some damn pancakes." He walked off, mumbling to himself. Jennifer watched the archer go then she turned to her friend.

"I didn't see anything that would make me worry about either of y'all." Jennifer comforted. Natasha sighed a bit.

"Oh. Good." She said. "In that case, let's go eat before Clint gets mad and then we can start figuring out where I go from here."

* * *

 **Review for me?  
Thank you for reading!  
**


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